Velvet is usually white, but anything is possible. If it is only one fish then you should isolate it. Start with doing daily water changes, raise up the heat. I don't like to treat unless I know exactly what it is, and it is so hard to diagnose fish with out actually seeing them. And I feel bad enough when I kill my own fish, so I am always hesitant when it comes to dianosing the problem. But velvet is a parasite, and it is on a cycle, so keep an eye in your original tank, if it is velvet it will come back.